Microsoft Monday announced a 40-fold increase in the online-file storage available for business versions of Office 365 and OneDrive, the company’s workplace document software and storage service.

The announcements, and Microsoft’s blog post on the topic, seem to be a declaration of war on Box and Dropbox, high-flying startups vying with Microsoft and others offering workplace tools like document sharing inside a company.

Microsoft didn’t call out Box or Dropbox by name in the text of the post. But its headline, “Thinking outside the box,” seemed a not-so-subtle jab at the new kids on the block.

Box Chief Executive Aaron Levie fired back in a blog post Monday night, criticizing Microsoft for keeping its storage software “closed” and making it difficult for users to move their data between different services. “Microsoft is stranding hundreds of millions of users and customers that have chosen Box, Dropbox, Google Drive, and others,” Levie wrote.

A spokesman for Dropbox declined to comment.

In the post, Microsoft argues that companies are better off buying an all-in-one product (from Microsoft of course) rather than stitching together technology pieces from multiple companies– Box for file storage, for example, plus Google Apps for document creation.

“The era of making isolated, single-solution decisions is rapidly coming to a close,” John Case, a corporate vice president for Microsoft Office, said in the post.

That one-stop-shop view runs counter to arguments of younger companies, such as Box or human-resources software firm Workday, which say corporations are better off with specialist software from firms focused on doing one thing.

This split in approaches to corporate technology is one of the fundamental philosophical battles as young and established companies fight over the $2 trillion companies spend each year on technology.

Box, and more recently Dropbox, have been adding offerings to stay ahead of deep-pocketed rivals like Microsoft. To differentiate itself, Box is pitching itself as a kind of hub for different types of business software, such as Salesforce.com 's programs for salespeople, and NetSuite’s financial software.

Dropbox, which initially focused on consumers, has begun targeting corporate customers with additional security features and tools for sharing documents.